1、 Work before use
1. Upon receipt of the new gel coat supply, check the following:
Quantity: whether it is consistent with the invoiced quantity; packaging: whether the packaging barrel is in good condition, product number, production batch number, to avoid the reception of temporary or overdue gel coat.
Examination of gel coat
2, storage:
Store the gel coat in batches in the warehouse, first in, first out; avoid direct sunlight; store in the original big and small barrels, tighten the cover; put the big and small barrels in parallel in order, and always store the curing agent separately from the gel coat and resin!
Gel coat
2、 Preparations
1. Mold pretreatment
A good mould is the key to produce high quality products; the mould must be cleaned and dusted thoroughly; the mould must be polished carefully and waxed; before using the new mould, a layer of release agent must be applied to ensure the smooth release; pay attention to the field operation environment to avoid the generation of dust on the surface of the mould;
2. Preparation of gel coat
Make sure that the color and type of the gel coat are correct, and the packaging barrel is not damaged; in order to achieve the same color, the whole set of products is best produced with the same batch of gel coat; before use, mix the gel coat evenly in the original barrel, but avoid over mixing; the best working temperature of the gel coat: 18-25 ℃; now the barrel of gel coat is ready to be taken for spraying, and use labor protection articles at any time!
Operation environment of gel coat
3. Inspection of spraying equipment
Check the oil and water removal of compressed air; inspect and clean the filter; select the size and angle of the spray nozzle according to the size and complexity of the mold; check and adjust the spray form.
Try to use the lowest pump pressure to press the gel into the spray gun; adjust the MEKP curing agent to the recommended quantity; if necessary, use gel time to calibrate the dosage of the curing agent for the spray gun; read the equipment instruction manual supplied by the equipment manufacturer carefully; and connect the spraying equipment at any time.
4. Preparation of spraying operator
Air mask or respirator; labor protection articles: clothing, gloves, glasses; it is very important for operators to use appropriate protection during spraying!
3、 Hand brush / spray operation
1. Preparation before hand brush operation:
Use a clean and soft high-quality long hair brush without shedding hair; pour out the required amount of gel coat in a clean barrel; add 1.5-2.5% MEKP curing agent, and mix it fully; mix the gel coat gently and thoroughly in the original barrel before use!
Suitable curing agent according to ambient temperature
2. Hand brush operation:
The brush should be continuously brushed to achieve a uniform thickness; the thickness of the gel coat should be checked at any time during operation; the 0.5-0.8mm thickness can not be reached at one time, and it can be brushed on the first layer after the gel. This requirement is higher than that of drawing.
3. Spraying operation:
Spray two or three times to establish the thickness of all coatings; the last spraying route must be perpendicular to the previous one; check the thickness of wet gel coat; the spray gun should be taken to the outside of the mold to stop; spray gel coat will be more uniform and save materials, but for the difficult part of the mold, brush in advance; usually the coating thickness is controlled at 0.5-0.8mm; The thickness depends on the end use of the product.
4、 Pre build up inspection
At the beginning of the reinforcement layer, the gel coat should be gelated to non cohesive (about 1.5 hours, at room temperature 23 degrees); the gel gel time in the deep groove of the mold needs to be lengthened; a gel can be accelerated by a small amount of ventilation or turning the mold; check whether all parts of the mold have been evenly gels, not to make the gel film curing too long or overnight.
Seal up
5、 Cleaning of tools
Clean the brush with cleaning agent in the cleaning room or container with cover; immerse the cleaned brush into the agent and cover the cover of the container; remove the nozzle of the spray gun and clean it with cleaning agent, and maintain the spraying equipment according to the requirements of the manufacturer;
What is a gel coat? Gel coat is a kind of colored thixotropic product, which is made of FRP and top coat by adding pigment and thixotropic agent into resin. Straight white point gel coat is a kind of resin added with pigments and auxiliaries, which is used for the surface of products and mainly plays the role of protection and beauty.
In the daily production, the gel coat we contact can be divided into mold gel coat and product gel coat. Although they only have a thin layer, it is not easy to do well. If every detail is not handled properly, it will bring big problems to the products. Wrinkle, orange peel, pinhole, micropore, crack, fisheye, sagging, poor glossiness and other problems often appear in our production, bothering everyone.
We know what is gel coat, and also understand the causes of problems in gel coat. Then I will answer this friend's question: why does the gel coat crack? Craze, that is, one of the cracks in the rubber coat. There are many reasons for the cracks on the surface of the products after forming, but there are four main reasons.
① Bad raw materials selected
The hardness, toughness and temperature resistance of the gel coat directly determine its quality. If the material is right, then the direction is right. Good hardness and toughness can make the rubber coat withstand certain external or internal stress, and good temperature resistance can withstand the impact of exothermic peak when the product solidifies.
② The coating thickness is too thin or too thick
If the thickness of the gel coat is too thin or too thick, it will also cause cracks, including the spray method of the gel coat. The normal thickness is 0.7-0.8mm for mold rubber coat and 0.4-0.6mm for product rubber coat. Especially if the spray is too thin, it is easy to produce cracks.
③ Transition layer problem
The so-called transition layer is the 2-3 layers pasted on the back of the gel coat (the first layer will generally be surface felt, and the second layer will be short cut felt). The transition layer is also very critical, because it is directly connected with the gel coat layer, and when its supporting force is insufficient, when the product surface is impacted, it is easy to produce cracks. Therefore, the material selection of the transition layer must be good. In addition, the connection between the transition layer and the gel coat surface also needs to be handled well, without layering.
④ Hit by an external force
External force impact is the main cause of cracks. Including knock during demoulding, impact during transportation, etc.
It's more important to know why the gel coat cracks, and how to avoid it. Now I will put forward my own opinions for your reference.
First of all, in terms of material selection, whether it's mold gel coat or product gel coat, we all try to choose some good materials, especially mold gel coat, with high reuse rate. It is not allowed to cause product quality problems due to cost factors.
② when spraying the gel coat, it is necessary to control the site environment and process flow. The site environment includes whether the operation site is clean, whether the temperature and humidity are appropriate, whether the air source is clean, etc., and the process flow should also be operated according to the specifications, and the spraying should be carried out twice. In order to ensure that the thickness of the gel coat is within the standard range, it is necessary to carry out quantitative spraying, that is, calculate the amount of gel coat required in advance according to the spraying area and thickness, so as to control the thickness of gel coat.
③ the resin of the transition layer should also be pasted with vinyl or m-benzene resin with better performance as far as possible. The so-called money should be spent on the cutting edge, but where it can't be saved, it still needs to be invested, one cent for each product. Grasp the time point of pasting. When the gel coat is not sticky, it is necessary to start pasting the transition layer. After each layer is solidified, pick bubbles, polish and paste the next layer. Make the work a little more detailed to ensure the high quality of the transition layer.
④ please avoid violence!!! As a manager, this should be strict with subordinates. It is difficult to demould, so you should do well in the waxing (demoulding agent) step. When it is difficult to demould, you should also use demoulding wedge and other tools, tap with rubber hammer or blow with air source to demould.
Source: composite community